Electronic apparatus which is remotely controllable, particularly entertainment electronic apparatus, is growing in popularity. Such entertainment electronic apparatus includes mainly television sets, video recorders, audio equipment, and the like. Remote-control devices are also used to control personal computers, garage door openers, roller blinds, and the like. Typically, remote control signals for the apparatus to be controlled are generated in response to the depression of keys on a remote control unit by the user and are transmitted to and decoded by a sensor circuit of the electronic apparatus.
Greater numbers of functions are continually being developed to control a single apparatus, e.g., a television which receives teletext in addition to the various television channels and which may be connected to a video recorder. Greater numbers of control commands are correspondingly required and necessitate an increased number of keys on the remote control unit. A reduction of the numbers of keys is possible by multiple key assignments or multiple key presses, however, the operation of the unit becomes correspondingly more complicated. A drastic reduction of the numbers of keys is not possible in this manner.
One solution to this problem is to provide interactive communication with the apparatus to be controlled, as is commonly used with computers. For example, the operator may be offered a "menu" of possible control commands via a display screen for the apparatus, and then chooses the desired command via a keyboard or a pointer device such as a "mouse". Movement of the position of the mouse on a surface results in an input of signals which determines the position of a cursor displayed on the display screen.
However, a mouse or other conventional pointer device requires cable attachment to the electronic apparatus or proximity of the operator to the display screen. In many situations, it is desireable to have a pointer device which is not attached to the apparatus and can be carried by the operator as a remote control unit. Remote control pointers are known which have a transmitter for emitting an ultrasonic or infrared signal which is received by the apparatus to be controlled. The amplitude and/or phase of the transmitted signal detected by a sensor of the apparatus varies depending upon the angular orientation of the pointer relative to its reference axis, and thereby the angular orientation of the pointer can be converted to position coordinates for a cursor on the display screen or to higher/lower, up/down, or left/right command signals for the apparatus to be controlled.
For example, as disclosed in U.S. Pat. No. 4,565,999, issued Jan. 21, 1986, to King et al., a "light-pencil" worn on the operator's head has a cluster of four LEDs with their principal axes uniformly diverging in horizontal and vertical directions from a central reference axis. The LEDs emit the same pulsed radiation pattern in timed sequence along their respective individual axes partially overlapping each other. The amplitude (intensity) of each signal at a sensor (phototransistor) on the reference axis varies with the angular orientation of the LED axis. Corresponding X and Y coordinates are computed based upon the relative amplitudes of the pointing signals with respect to its opposite pair in the horizontal and vertical directions. However, this arrangement has the problem that use of the device at varying distances from the apparatus encounters difficulty in preserving the amplitude proportionality of the signal samples, as well as places linearity and stability constraints on the receiver circuitry.
A modified remote control pointer device is disclosed in U.S. Pat. No. 4,745,402, issued May 17, 1988, to Auerbach. The pointer array has eight LEDs arranged symmetrically in the horizontal and vertical plane directions about a reference axis. In each line, a center LED has a pair of LEDs pointing in opposing angular directions from its center axis. The pulses emitted by each opposing pair are shifted opposite in phase, such that the phase angles of the resultant combined signals received at the receiver inversely correspond to the angular orientation of the pointer in the horizontal and vertical directions. However, this arrangement has the disadvantage that the multiplicity of LEDs and signal samples results in a bulky remote control unit and complexity of signal processing and conversion.